1. Field of the Invention
This invention relates to emergency call systems (e.g., E9-1-1), including wireless and Internet Protocol (IP) based Voice Over Internet Protocol (VoIP) emergency call systems, that rely on non-call associated signaling in order to provide location data.
2. Background of the Related Art
9-1-1 is a phone number widely recognized in North America as an emergency phone number that is used to contact emergency dispatch personnel. Enhanced 9-1-1 (E9-1-1) is defined by an emergency call being selectively routed to an appropriate PSAP, based on a special identifier (P-ANI, or “Pseudo Automatic Number Identifier”, also referred to as “ESxK”), and includes the transmission of callback number and location information when 9-1-1 is used. E9-1-1 may be implemented for landline, cellular or VoIP networks. A Public Service Answering Point (PSAP) is a dispatch office that receives 9-1-1 calls from the public. A PSAP may be a local, fire or police department, an ambulance service or a regional office covering all services. As used herein, the term “PSAP” refers to either a public safety access point (PSAP), or to an Emergency Call Center (ECC), a VoIP term.
Regardless of the network type, a 9-1-1 service becomes E-9-1-1 when automatic number identification and automatic location information related to the call is provided to the 9-1-1 operator at the PSAP. A primary challenge results from the fact that calls may arrive at the PSAP without the caller's actual callback number or location information displayed at the emergency operator's terminal.
FIG. 3 shows a conventional landline public safety access point (PSAP) to automatic location identifier (ALI) connection.
In particular, FIG. 3 shows a PSAP 400 connected to one Automatic Location Identifier (ALI) database 401. Upon receiving a 9-1-1 call, the PSAP 400 queries the ALI 401 for location data. The ALI database 401 accepts the query from the PSAP 400 for location. The query includes the telephone number of an emergency caller. The ALI database 401 relates the received telephone number to a physical street address and provides that street address (location information) back to the PSAP 400 in a manner that works for the customer premise equipment (CPE) display at the PSAP 400.
An ALI is typically owned by a local exchange carrier (LEC) or a PSAP, and may be regional (i.e. connected to many PSAPs) or standalone (i.e. connected to only one PSAP). There is currently no one single standard interface protocol for PSAP-ALI connection/communication.
FIG. 4 shows a context diagram for a conventional non-landline positioning center (e.g., an Internet based voice over Internet Protocol (VoIP) positioning center).
In particular, the ALI database 401a includes a conventional emergency services key (ESQK or ESRK) in a location request sent to an appropriate positioning center 402 (XPC). The emergency services key (ESQK or ESRK) is used by the positioning center 402 as a key to look up the location and other call information associated with the emergency call.
In non-landline telephony, the PSAPs 400a query the ALI 401a for location information. However, the ALI 401a is not pre-provisioned with location data for non-landline calls (e.g. cellular, VoIP etc) and must communicate with other network entities to obtain and deliver location data to the PSAP 400. Non-landline telephony standards (e.g. cellular, VoIP etc) have mandated that ALIs 401a maintain connectivity to a positioning center 402 that is able to provide current location data for a non-landline call. In the current state of technology, the positioning center 402 provides the caller's location and the callback number to the ALI, which passes it to the requesting PSAP. As can be seen in FIG. 4, an ALI may maintain connectivity to more than one positioning center via multiple interface types—both standard and non-standard (e.g. NENA-02, E2/E2+N-E2(ESP), PAM, etc.).
As used herein, the generic term “XPC” refers interchangeably to any standards-based positioning center. As examples, a positioning center 402 may be any one of the following types used in non-landline networks:                GMLC (Gateway Mobile Location Center): The positioning center that retrieves, forwards, stores and controls emergency position data within the GSM location network.        MPC (Mobile Position Center): The positioning center that retrieves, forwards, stores and controls emergency position data within the ANSI location network.        VPC (VoIP Positioning Center): The positioning center which retrieves, forwards, stores and controls emergency position data within the VoIP location network.        
The term “XPC network” is used herein when appropriate to refer to any non-landline network where a positioning center 402 responds to ALI queries including an emergency services key for location, e.g., cellular, VoIP etc.
In the process of handling an emergency call, a first responder (or responders) may be dispatched to the caller's location. Typically, the dispatcher at the Public Safety Answering Points (PSAPs) determines the appropriate first responder(s), and makes contact with a dispatcher for the appropriate first responder. After contact, the PSAP dispatcher (and/or the dispatcher for the first responder) conveys relevant location information to the first responder.
Using conventional techniques, most PSAPs rely on the age-old method of verbally relaying caller Automatic Location Identification (ALI) data to the first responder, i.e., speaking the caller's location information over a voice phone call between the PSAP and the first responder.
While many police and fire department vehicles do have wireless data transfer capabilities, such services are typically used to interact with local or regional databases to check license plates, criminal records, outstanding warrants, etc. No conventional method exists to use wireless data transfer capabilities for downloading ALI data relating to a PSAP's emergency call to a first responder.
While the next generation of E911 services has promised to facilitate the delivery of caller information (name, address, phone number, medical conditions, etc) from an emergency caller to the PSAP, little progress has been made in the second leg of communication, i.e., in relaying this caller information as digital data from the PSAP to the relevant first responder (e.g., police, fire, or medical).
Needless to say, while serving the purpose, verbal relay of location information is slow and prone to error. At best, verbal transfer of ALI information from a PSAP to a first responder delays a lifesaving response, and at worst can result in the dispatch of a first responder to a wrong address.
There is a long felt but unsolved need for efficient transfer of location information relating to a PSAP's emergency call from the PSAP to a first responder.